Fume hood incorporating high efficiency auxiliary air plenum

Abstract

An auxiliary air fume hood provided with an improved airflow system for controlling the passage of air through an auxiliary air housing and orienting the flow of air in front of the face of the hood. The hood is designed to capture the auxiliary air through the face of the hood when the temperature of said air is as much as 20° F. higher than the room air temperature.

We claim: 
     
       1. A fume hood comprising a frame including top, rear, and side panels, and an air exhaust opening; a bypass opening on the front portion of the hood; an auxiliary air housing mounted on the uppermost portion of the front of the hood and extending outwardly therefrom; and an access opening on the rear portion of the auxiliary air housing which is disposed at the bypass opening of said hood; wherein said housing further comprises an auxiliary air supply opening; a primary means for diffusing a downward flow of air from the air supply, said primary means disposed adjacent to the auxiliary air supply opening; a secondary means for diffusing the downward flow of air, said secondary means positioned below the primary means; a tertiary means for diffusing the downward flow of air and directing the passage of said air flow in front of the front portion of the hood, wherein said tertiary means includes a downwardly depending baffle which slopes downwardly away from the front of the hood from an area directly above said bypass opening; said baffle comprising a perforated support member having a layer of porous diffuser material thereon; said support member having a perforated rear portion disposed immediately in front of the upper margin of said bypass opening which is free of said diffuser material; said baffle also including a front portion extending along the lower forward margin thereof providing a second layer of diffuser material; said front portion of said baffle and said rear portion of said support member each having a length constituting a minor portion of the length of said baffle measured from front to rear thereof. 
     
     
       2. The fume hood of claim 1 wherein said rear portion of said support member free of said diffuser material has a length of about 17% of the length of said baffle. 
     
     
       3. The fume hood of claims 1 or 2 in which said front portion of said baffle extending along the lower forward margin thereof has a length of about 17% of the length of said baffle.